Full header support HTTP HEAD Resource requests

Allow the body to be written in order for all headers to be set
as they would be on HTTP GET. The body content is ignored as a
lower level.

See gh-25976

Author: rstoyanchev

spring-webflux/src/main/java/org/springframework/web/reactive/resource/ResourceWebHandler.java

@@ -355,11 +355,6 @@ public Mono<Void> handle(ServerWebExchange exchange) {
 						setHeaders(exchange, resource, mediaType);
 
 						// Content phase
-						if (HttpMethod.HEAD.matches(exchange.getRequest().getMethodValue())) {
-							exchange.getResponse().getHeaders().set(HttpHeaders.ACCEPT_RANGES, "bytes");
-							return Mono.empty();
-						}
-
 						ResourceHttpMessageWriter writer = getResourceHttpMessageWriter();
 						Assert.state(writer != null, "No ResourceHttpMessageWriter");
 						return writer.write(Mono.just(resource),

spring-webflux/src/test/java/org/springframework/web/reactive/resource/ResourceWebHandlerTests.java

@@ -123,10 +123,6 @@ public void getResourceHttpHeader() throws Exception {
 		assertThat(resourceLastModifiedDate("test/foo.css") / 1000).isEqualTo(headers.getLastModified() / 1000);
 		assertThat(headers.getFirst("Accept-Ranges")).isEqualTo("bytes");
 		assertThat(headers.get("Accept-Ranges").size()).isEqualTo(1);
-
-		StepVerifier.create(exchange.getResponse().getBody())
-				.expectErrorMatches(ex -> ex.getMessage().startsWith("No content was written"))
-				.verify();
 	}
 
 	@Test

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -511,10 +511,6 @@ public void handleRequest(HttpServletRequest request, HttpServletResponse respon
 		setHeaders(response, resource, mediaType);
 
 		// Content phase
-		if (METHOD_HEAD.equals(request.getMethod())) {
-			return;
-		}
-
 		ServletServerHttpResponse outputMessage = new ServletServerHttpResponse(response);
 		if (request.getHeader(HttpHeaders.RANGE) == null) {
 			Assert.state(this.resourceHttpMessageConverter != null, "Not initialized");

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandlerTests.java

@@ -118,7 +118,6 @@ public void getResourceHttpHeader() throws Exception {
 		assertThat(this.response.getDateHeader("Last-Modified") / 1000).isEqualTo(resourceLastModified("test/foo.css") / 1000);
 		assertThat(this.response.getHeader("Accept-Ranges")).isEqualTo("bytes");
 		assertThat(this.response.getHeaders("Accept-Ranges").size()).isEqualTo(1);
-		assertThat(this.response.getContentAsByteArray().length).isEqualTo(0);
 	}
 
 	@Test
@@ -686,6 +685,20 @@ public void partialContentByteRangeWithEncodedResource(GzipSupport.GzippedFiles
 		assertThat(this.response.getHeaderValues("Vary")).containsExactly("Accept-Encoding");
 	}
 
+	@Test // gh-25976
+	public void partialContentWithHttpHead() throws Exception {
+		this.request.setMethod("HEAD");
+		this.request.addHeader("Range", "bytes=0-1");
+		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "foo.txt");
+		this.handler.handleRequest(this.request, this.response);
+
+		assertThat(this.response.getStatus()).isEqualTo(206);
+		assertThat(this.response.getContentType()).isEqualTo("text/plain");
+		assertThat(this.response.getContentLength()).isEqualTo(2);
+		assertThat(this.response.getHeader("Content-Range")).isEqualTo("bytes 0-1/10");
+		assertThat(this.response.getHeaderValues("Accept-Ranges")).containsExactly("bytes");
+	}
+
 	@Test  // SPR-14005
 	public void doOverwriteExistingCacheControlHeaders() throws Exception {
 		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "foo.css");